Ericsson Updated ECP-206 Exam Questions and Answers by mikayla

The function of LSR from an LDP perspective is to distribute labels of FEC to its LDP peers. LSR stands for Label Switching Router, which is a router that forwards packets based on labels rather than IP addresses in an MPLS network. LDP stands for Label Distribution Protocol, which is a protocol that distributes labels for MPLS forwarding along the shortest path calculated by an IGP. FEC stands for Forwarding Equivalence Class, which is a group of packets that are forwarded in the same manner by an LSR. An LSR uses LDP to advertise the label mappings for each FEC to its LDP peers, which are other LSRs that have established an LDP session with it12.

References: Ldp | Microsoft Learn, Label Distribution Protocol - Wikipedia

The correct order of DiffServ priority (highest to lowest) for the DiffServ classes: Default Forwarding (DF), Network Control (NC), Assured Forwarding (AF), and Expedited Forwarding (EF) is EF, NC, AF, DF. DiffServ is a QoS model that classifies and prioritizes traffic into different service classes based on the DSCP field in the IP header. The DSCP field is a 6-bit field that can encode up to 64 different per-hop behaviors (PHBs). The DiffServ classes are predefined groups of PHBs that have similar characteristics and requirements. The four main DiffServ classes are:

• EF: This class provides the highest priority and lowest delay for real-time applications such as voice and video. The DSCP value for EF is 101110 or 46 in decimal12.
• NC: This class provides the second highest priority and low delay for network control traffic such as routing protocols and network management. The DSCP value for NC is 110000 or 48 in decimal12.
• AF: This class provides four levels of assured forwarding with different drop probabilities for each level. AF is suitable for applications that require guaranteed bandwidth and delivery assurance, such as web browsing and email. The DSCP values for AF range from 001010 to 011110 or 10 to 46 in decimal12.
• DF: This class provides the lowest priority and best-effort service for applications that can tolerate packet loss and delay, such as file transfer and backup. The DSCP value for DF is 000000 or 0 in decimal12.

References: Differentiated Services - Wikipedia, DSCP - Differentiated Services Code Point - Mpirical

Two roles of the DHCP protocol in a network are:

• It is used by hosts to obtain the IP address and other parameters from the DHCP server. DHCP stands for Dynamic Host Configuration Protocol, which is a protocol that provides automatic and centralized management of IP addresses and other network configuration parameters for devices connected to a network. A host that needs an IP address can send a request to a DHCP server, which will assign an available IP address from a pool and lease it to the host for a certain period of time34.
• It is used to inform hosts about the default gateway. The default gateway is the IP address of the router that connects the host to other networks. The default gateway is one of the parameters that can be delivered by the DHCP server to the host, along with other parameters such as subnet mask, DNS server, domain name, etc. The host can use the default gateway to send packets to destinations outside of its local network34.

References: What Is DHCP? (Dynamic Host Configuration Protocol) - Lifewire, Dynamic Host Configuration Protocol - Wikipedia

Referring to the exhibit, the correct statement is that the service provider’s P routers are not aware of the customers’ routes. This is because P routers only need to forward MPLS packets based on their labels, without looking into their IP headers or VPN information. The P routers do not have any VRFs configured for the customers, nor do they participate in MP-BGP sessions with other PE routers. The PE routers are responsible for maintaining VRFs for each customer and for exchanging VPN routes with other PE routers using MP-BGP910.

References: Layer 3 VPNs (L3VPN) - Cisco, MPLS VPN - Wikipedia